Solve for $q$ : $-20 = -24 + q$
Solution: Add $24$ to both sides: $ \begin{eqnarray} \\ \hphantom{-20 {+ 24}} &\hphantom{=}& \hphantom{q} \\ -20 &=& -24 + q \\ \\ {+24} && {+24} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ -20 {+ 24} &=& q \\ \end{eqnarray} $ Simplify. $ q = 4$